iCal Sync creates strange duplicates with every sync

I read quite a few threads here as well as googled for my problem, but none of the solutions helped. I don't know if it's just a sync error or more to it, but this is happening (it started probably after updating to iOS 6.1 - before that everything was fine):

Usually syncing between my Macbook Pro and my iPhone 4S was flawless. If I made changes in my iCal on my iPhone I could see the new events on my Macbook Pro iCal as well (after the sync obviously) and the same vice versa.

However, after the update (I suppose) to iOS 6.1 all the changes that I made to my iCal on my iPhone didn't sync anymore to my iCal on my Macbook Pro. If I added a new event on my Macbook Pro iCal it was synced to my iPhone 4S - so far so good. However, if I make a change to an already existing event in my iCal on my MBP and then sync with my iPhone again it doesn't apply the change on my iPhone, but creates a new event.

So, in most cases I change the time of the event, but instead of syncing the new time a new event is created. The same goes if I change the location or name. The time stays the same, but a new event is created with the changed name and suddenly I have to events at the same time.

Meanwhile my iPhone iCal is devastated with events all over the place so that there's no use possible.

I checked all my settings in iTunes as well as on my iPhone, but can't find any setting wrong.

not really clear how it is caused. What OS do you have on the computer?

If the calendar in your computer is OK, and your calendar in the phone is mixed up with faults: connect the phone to iTunes, set auto sync to off, then in the info page bottom in "advanced" check "calendars" to replace items in the iphone, then click sync; it does replace the calendar completely, and once again all is equal. It automatically unchecks this after the sync.

Is your calendar in the mac OK? if so export an archive, look where it goes, write that down.

Then Quit the calendar from the menu.

The iPhone: hold both the Power and Home buttons at the same time, keep holding, until you see the white apple logo and then let go. let it start completely.

1. Start iTunes on the mac, connect the iPhone, uncheck "sync automatically", check "calendar" in the "advanced" paragraph on the bottom of the "info" page, then sync. The iOS calendar should now be correct again. Check that.

If not correct post that here with the #1 as identifier.

2. If correct, make or change one calendar entry in the Mac in tomorrow's day. Then sync, is that change coming correct in the iOS calendar? If not post it here #2.

3. If it is correct, make a new entry for tomorrow in the iOS calendar. then sync. Is that correct?

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